[Response of radial growth of Pinus sylvestriformis and Picea jezoensis to climate warming in the ecotone of Changbai Mountain, Northeast China].

Changbai Mountain is a typical distribution area of temperate coniferous and broad-leaved mixed forests, with significant influence of global climate change. In order to understand the responses of forest ecosystem to climate change, we examined the responses of dominant arbor species in the community ecotone of broad-leaved Korean pine forest and spruce-fir forest (also known as dark coniferous forest), Pinus sylvestriformis and Picea jezoensis. The standard chronologies were established by obtaining tree ring width data in order to identity the key climatic factors that confine the radial growth of both species. The responses of P. sylvestriformis and P. jezoensis to climate factors were different.P. sylvestriformis was more sensitive than P. jezoensis, indicating that P. sylvestriformis was more suitable for dendroclimatological analysis. The radial growth of P. sylvestriformis was consistent with the increases of mean temperature, while the radial growth of P. jezoensis showed a "divergence problem" which decreased with the increases of mean temperature. The radial growth of P. sylvestriformis was mainly limited by temperature, especially the mean temperature in last July and August and current September. However, there was a negative correlation between standard chronologies of P. jezoensis and mean temperature in most months, which was limited by both temperature and precipitation. The correlation between radial growth of both species and climate factors after sudden temperature rise, was weaker than that before sudden temperature rise. The correlation between radial growth and climate factors changed from positive to negative in some months. Current temperature rise might not exceed the critical threshold of the radial growth of P. sylvestriformis, which could promote the radial growth. In addition, the wavelet analysis showed that the radial growth of trees in this area might be affected by large-scale coupling effects of atmospheric-ocean-land changes. In conclusion, climate warming was beneficial to the radial growth of P. sylvestriformis, while drought stress caused by warming was the main factor limiting the radial growth of P. jezoensis. If the global temperature continues to increase in the future, it will have an adverse impact on P. jezoensis. The results would help improve our understanding of the responses of radial growth of P. sylvestriformis and P. jezoensis to future climate change, and provide some basic data for climate reconstruction using both species.